Angraecum
Angraecum, commonly known as the comet orchid, is a diverse genus of orchids native to tropical and South Africa, Madagascar, and Sri Lanka. These plants are characterized by their fleshy leaves, adapted to dry tropical woodlands, and their distinctive flowers, often white with a long spur at the base of the lip, which can be up to 30 centimeters long in some species. This unique morphology has led to fascinating co-evolutionary relationships with specific pollinators, most famously the hawk moth with Angraecum sesquipedale.
Key Facts
- ›The genus Angraecum is native to tropical and South Africa, Madagascar, and Sri Lanka.
- ›Most Angraecum species are epiphytic, growing on trees, though some are lithophytic, growing on rocks.
- ›Flowers are typically white, with some variations in yellow, green, or ochre, and feature a prominent spur.
- ›Angraecum sesquipedale is famous for its exceptionally long spur, which Darwin predicted would be pollinated by a moth with a similarly long proboscis.
- ›Many Angraecum species are threatened and protected under CITES due to over-collection and habitat loss.
Comet Orchid
Epiphytic, Lithophytic
Late Winter, Spring
Loose, Free Draining
Hawk Moth, Bird, Cricket, Lizard
About Angraecum
Overview
The genus Angraecum, commonly known as the comet orchid, encompasses a diverse group of orchids native to tropical and South Africa, Madagascar, and Sri Lanka. With 223 recognized species, Angraecum exhibits considerable variation in both its vegetative and floral characteristics, largely adapted to dry tropical woodland habitats. This adaptation is reflected in their fleshy leaves. Most species are epiphytic, growing on trees, while a few are lithophytic, adhering to rocks.
Flowers and Pollination
Angraecum flowers are typically borne in racemes from the leaf axils and are generally long-lasting. The predominant color is white, although some species present flowers in shades of yellow, green, or ochre. A defining feature of Angraecum flowers is the presence of a long spur extending from the back of the labellum (lip). The most famous example is Angraecum sesquipedale from Madagascar, which possesses a spur up to 30 centimeters long. This extreme morphology led Charles Darwin to predict the existence of a pollinator with a similarly long tongue, a prediction famously confirmed with the discovery of the hawk moth Xanthopan morganii praedicta. Other Angraecum species have evolved different pollination strategies, with reports of bird pollination in Angraecum striatum and cricket pollination in Angraecum cadetii.
Distribution and Taxonomy
The genus was described by Jean-Baptiste Bory de Saint-Vincent in 1804, with Angraecum eburneum serving as the type species. The name "Angraecum" is a Latinization of the Indonesian and Malay word "anggrek," meaning "orchid." While the majority of the genus is distributed across tropical Africa and Madagascar, an outlier species is found in Sri Lanka. These orchids typically inhabit humid regions at elevations ranging from sea level up to 2,000 meters.
Conservation
Many species within the Angraecum genus face significant threats and are considered at risk of extinction. Consequently, they are protected from international trade under CITES. The genus is recognized by the IUCN Orchid Specialist Group as a high conservation priority. Endemic species, particularly those in Madagascar like Angraecum sororium, are vulnerable to over-collection, habitat loss, fragmentation, and the impact of fires, alongside the decline of their specialized pollinators.
Horticulture
In cultivation, Angraecum orchids are typically abbreviated as Angcm. They flower best in bright, indirect light, and direct sunlight should be avoided as it can cause severe leaf damage. Waterings should be thorough, ideally in the morning, to prevent fungal issues, and the potting mix should be loose and well-draining, suitable for epiphytic growth. Some hybrid varieties, such as Angraecum Veitchii, are known for producing blooms annually and possess a strong, heady fragrance, often released at night. Due to their substantial root systems and potential top-heaviness when mature, heavy pots or added weight are recommended to ensure stability.
Source: Wikipedia ↗
Frequently Asked Questions
What are comet orchids?
Comet orchids are commonly known as Angraecum, a genus of orchids found in tropical and South Africa, Madagascar, and Sri Lanka. They are recognized for their fleshy leaves and distinctive flowers, often white with a long spur.
Where do Angraecum orchids grow naturally?
Angraecum orchids are native to tropical Africa and Madagascar, with one species found in Sri Lanka. They can also be found on the Comoros, Seychelles, and Mascarene Islands, typically growing in humid regions between sea level and 2,000 meters.
What is unique about the flowers of Angraecum sesquipedale?
The flower of Angraecum sesquipedale is remarkable for its exceptionally long spur, measuring up to 30 centimeters. This extraordinary length led Charles Darwin to hypothesize the existence of a pollinator with a correspondingly long tongue, a prediction later confirmed with the discovery of the hawk moth Xanthopan morganii praedicta.
Are Angraecum orchids endangered?
Yes, many species of Angraecum orchids are considered at risk of extinction in the wild. They are protected under CITES due to threats such as over-collection, habitat fragmentation, and loss of their specific pollinators.
How should I care for an Angraecum orchid?
Angraecums thrive in bright, indirect light, avoiding direct sunlight which can damage their leaves. They prefer loose, free-draining potting media and regular watering, ensuring thorough soaking to flush out fertilizer salts. Watering in the morning is recommended to prevent fungal rot.
What are the different pollination methods for Angraecum orchids?
While moth pollination is famously associated with Angraecum sesquipedale, other species exhibit different pollination strategies. For instance, Angraecum striatum is pollinated by birds, and Angraecum cadetii is pollinated by crickets.
Related Orchid species
Jumellea
Jumellea is a genus of orchids comprising 55 species, primarily found in Madagascar, the Comoros, Mascarenes, and eastern Africa. Named in honor of French botanist Henri Lucien Jumelle, these orchids often display adaptations for pollination by hawk moths, though self-pollination is also observed in some species like Jumellea stenophylla.
Agrostophyllum
Agrostophyllum is a genus of approximately ninety orchid species belonging to the family Orchidaceae, characterized by their grass-like leaves and distinctive ball-like inflorescences. These orchids are primarily epiphytic, found in tropical lowland forests across a wide range from the Seychelles and Madagascar to the Pacific Islands, with a significant center of diversity in New Guinea.
Galeola
Galeola is a genus of myco-heterotrophic orchids found across Southeast Asia, Madagascar, and the Comoros. These orchids are of particular biological interest due to their parasitic nature, relying entirely on fungi for sustenance, and their exceptionally large, winged seeds, which are the biggest among all orchid seeds.